I think I need a rebuild... what went wrong? - Snowmobile Forum: Your #1 Snowmobile Forum

rotaxryder · 01-05-2005, 09:35 PM

Sled I'm referring to is a 92 Formula Plus 583 with 5,000 miles on it. Took it out for the first ride of the season last week. It started right up with fresh gas. Seemed to have plenty of power and I was easily doing 80 mph across the lake...all of a sudden it just killed instantly, didn't miss or sputter, just instantly died. I couldn't hear any noise bad noise at all except what I think was my clutch winding down. Pulled the plugs and found there was very weak spark or none at all. Engine not locked up. Pulled hard like it always has...Tried forever to get it to start but it was a no-go. The exact same thing happened to me last year (died like that at high speed) but I was able to restart it after putting new plugs in, after it cooled down and it ran fine, thought coil must be going out. Replaced the coil with a different one and it still wouldn't start but now seems like I'm getting good spark.

Tested compression, cyl #1: 140+psi cyl#2 hardly anything at all maybe 10 lbs or so ouch!
Pulled the head and dumped coolant everywhere...
First cylinder lookes perfect 2nd had several scratches just deep enough to catch a fingernail, Piston looks good, rings actually look like they are still making a decent seal. So thats probably the only problem then? I just need to rebuild the top end? Even if the pison/rings look fine and the scratches don't look too big on the cylinder that explains only 10psi???
Any ideas on why this happened?? Would a instant motor shutoff at very high rpms cause this? Just plain worn out at 5k miles?

Thanks in advance for any help!

YamahaVector · 01-05-2005, 09:50 PM

How long do you warm your sled up for when you start it? It sounds like you cold siezed the engine a couple of times. This would explain the engine quiting and the scratches on the cylinder.

skidoobudman8 · 01-05-2005, 09:59 PM

vector has some good points, but I believe at or around 5 thousand miles, your definetely "riding on borrowed time". With that being said, I am guessing that the engine had no prior engine work done to it. With the high milege, and then just blasting it out on a lake, that might have been all it took. Like you said, maybe it is just done.

rotaxryder · 01-05-2005, 11:04 PM

I always allowed plenty of time for it to warm up before hitting the higher revs. Nope I don't think its ever needed engine work before.

Instead of buying new pistons (probably will end up doing anyway) when the stock ones seem to be in good shape (will confirm upon further inspection)... Can i just bore out the cylinders and re-ring the stock pistons? Is their another cheaper alternative?

**smallengineguy** · 01-06-2005, 06:28 AM

If the scratches are very minor, usually just a heavy honing will do it. I just did a Yamaha that had several scratches on it, just a home honing brought the compression from 60 to 140 lbs. Buy a standard size ring set and top end gasket set for it, and you should be all set. If the piston is dinged up, replace that also.

rotaxryder · 01-06-2005, 11:19 PM

I think the scratches might be a little bit deep for honing but I'm not sure. If i do have to have the cylinders bored out slightly and decide I want to use the OEM pistons where can i find oversize rings? Dealer only? Also does Wisco sell oversize rings for their standard bore pistons? Might be able to pick up a pair of used ones cheap...

Thanks for your help.

**smallengineguy** · 01-07-2005, 06:08 AM

They don't make oversize rings for standard pistons. You just go up one size on everything. They make .010 and .020 kits. Cast piston kits are like $50. Wiseco forged kits are around $100. Either kit comes with piston, rings, pin and clips. You'll still need a top end gasket set.

1994VMAX · 01-07-2005, 08:52 AM

This might not be your situation, and you might have pulled the pots and figured this out by now, but, did you snap off a piston skirt? High mileage engines like that can tend to wear and the piston will not be as tight in the pot as it was when it was new. This can cause the piston to rattle in there a little bit and the piston skirts take most of the force, thus snapping them off. Just something to look into. Parts of the piston can find their way up to the top of the piston and do some damage too. Just something to look for.

It happened to me once, and it melted part of the piston skirt to the rings. This is why I had real crappy compression of about 20 or 30 lbs.

rotaxryder · 01-07-2005, 10:02 PM

Appreciate your help as I'm no mechanic. Just a novice who wants to try doing something for myself...Nope, no snapped piston skirt. When I had just the head off I pulled it over and the "bad" cylinder was not getting the top of the piston wet with gas and atomizing fuel like the "good" side was. I pulled the carb on that side and cleaned it but still no differece. I think the gas is just going into the case...Probably because that cylinder and piston are messed up? I think I'm just going to rebuild it and hope for the best (no failures)

Anyway I just bought 2 standard bore 583 cylinders off a parts sled on ebay and I'm just going to use those instead of honing/boring my existing ones. I got them cheap enough...

Do I have to tear into the case to look for metal shavings? I was told I probably didn't have too... I found a few tiny peices that were sitting in the top of a grove in the case and a couple tiny flakes. I vaccumed/cleaned everything out as best as I could but I know I probably din't get everything. Could I just try to flush out the case with gas? Is there a drainplug for the case on 583s?

**smallengineguy** · 01-07-2005, 10:17 PM

There is no drainplug in the case. If you remove the pistons you should be able to see the bottom of the case when you turn the crank. Use a magnet on a stick thingy to see what you pick up. Use carb cleaner to spray the inside down. Shove paper towels down inside the case to absorb the dirty cleaner and then re-magnet again to pick up whatever ran to the bottom with the cleaner.

Rev. Ronnie · 01-08-2005, 02:09 AM

You can't bore the cylinders and use stock, non oversize pistons.

If you bore the cyl. you must also use a oversize piston. I thought this was pretty much a given?

The old, Model-T thinking, knurled piston, oversize ring mentality may be confusing you

but with a high performance two stroke, .015 piston to wall clearance spells disaster.....in any language.

rotaxryder · 01-08-2005, 09:43 PM

Thanks smallengineguy I'll try the magnetic probe. Never thought of that. Btw how are those PRS front shocks I sold you last year working out?

Lol yeah Rev. Ronnie. My dad is actually the one who told me I could get oversize rings. He used to race cross country and had a Cat Z with custom suspension back in the day that he says he redid the topend after boring it out with oversize rings and it ran great afterward but blew up again from running too hot (air cooled) His memory isn't the best...

**smallengineguy** · 01-08-2005, 10:28 PM

Ahhh...So that's you! I just put them in last month...Haven't ridden enough to tell yet. Hopefully tomorrow I'll be able to tell! Great shock, though!

rotaxryder · 01-24-2005, 09:31 PM

Yup thats me lol, hope those shocks got to be used recently... Anyways I haven't gotten around to finishing the sled yet but I should have all the parts to redo the topend finally here by the end of this week and I have a couple questions:

-What are the torque specs for the 583 jugs and the head?
-The case is completly dry and as clean as I could get it. Do I need to put any lube like oil or gas in it before startup? (I will be oiling up the pins and cylinders walls well with regular 2 stroke oil)
-Can I intially start the sled without coolant and add it later if everything works out well, making sure things don't get too hot?
-Regular "car" coolant will work fine won't it? 50/50 water mix??

I think putting everything together should be pretty straight forward (I hope) Just install the pistons/needlebearings/pins on the rods, carefully spread the rings apart and fit into pistons, let pistons rest on a couple blocks of wood and slip cylinders over them while carefully compressing the rings with thumbs. Torque down, add coolant?, replace exhaust, airbox, ect., start it up and break it in carefully!.... Sound right?

Really do appreciate your help with my first topend job on a sled!

**smallengineguy** · 01-25-2005, 06:59 AM

Yup, that's the way! Put some mixed fuel in the tank to go along with the oil injection. The engine assembly lube is all you'll need to start it, you don't need to put anything else in. Put 50/50 coolant in it before you start it. That will allow everything to seat in correctly. Use silicone sealer around the head bolts to prevent coolant leaks. Torque to 16 ft lbs.

The shocks work great! Good luck!

mysunnshine · 01-25-2005, 08:31 AM

A magnet will not pick up aluminum chips from a piston or crankcase. If there is actual steel filings in the motor you need to look further into the repair....

Sunshine

BLinindoll · 01-25-2005, 08:14 PM

woah... phoenix? do much sledding out there?

mysunnshine · 01-26-2005, 08:00 AM

Some... We head up north to Flagstaff at 7500ft elevation. This year has been good for sledding.....

rotaxryder · 02-11-2005, 01:05 PM

Finally got everything back together with new rings and used cylinders/used pistons from another sled. Wouldn't start. Compression was 130lbs on the left side (formerly like 20) and about 60 on the right side

(formerly about 130). With tons of starting fluid I finally got it to run later on (started hard) but it didn't idle. So chances are I bought crap parts or is there anything else I can check? Head gasket blowing out air, etc? Rings seemed to make a good tight seal in the cylinders and I lubed everything up well. Anything else I can check?

Thanks for the help.

yamahog · 02-12-2005, 10:23 AM

That doesn't sound to good. The one cylinder has about 60 psi. That would be why it wouldn't start. Maybe you should have both cylinders bored then get some new pistons. It sounds like your luck is about as good as mine.